Haplotype M2 in the annexin A5 (ANXA5) gene and the occurrence of obstetric complications

Inherited or acquired thrombophilias have been largely explored as a cause of pregnancy complications. However, pathogenesis of obstetric complications, as fetal loss and pregnancy-related hypertensive disorders is still partly unexplained. Recently, a common haplotype (M2) within the annexin A5 (ANXA5) gene has been described as a risk factor in recurrent fetal losses (RFL). It has been demonstrated to reduce the promoter activity of the ANXA5 promoter in luciferase reporter assays. Aim of this study was to investigate the prevalence of M2 haplotype in three different settings of women with previous obstetric complications: RFL, intra-uterine fetal death (IUFD) and pregnancy-related hypertension (gestational hypertension [GH] and pre-eclampsia [PE]). One hundred three patients with previous RFL, 54 with IUFD, 158 with hypertensive disease (67 GH, 91 PE) were investigated. As controls, 195 women from the same ethnic background with uneventful pregnancies were enrolled. Logistic regression, correcting for age, gravidity and parity showed that the ANXA5 haplotype is significantly and independently associated with the occurrence of RFL (3.1; 95%CI: 1.1-9.5; p=0.047) and pregnancy-related hypertensive disorders (2.1; 95%CI: 1.2-3.5; p=0.008). The M2 haplotype might be a new and relevant risk factor for obstetric complications.